The present invention relates to an image-taking apparatus, and more particularly to an image-taking apparatus that enables a user to arbitrarily switch a viewfinder mode by operating a mirror unit.
A single lens reflex camera as one image-taking apparatus reflects the light emitted from an image-taking lens via a mirror closer to an image surface than the image-taking lens, and introduces the light to the optical viewfinder (“OVF”). Thereby, a photographer can view an erect object image formed by the shooting lens. The mirror is obliquely provided on a shooting optical path.
In shooting an object image, the mirror retreats from the shooting optical path, and enables the light from the image-taking lens to such an imaging medium as a film and an image-pickup device, such as a CCD. After the shot, the mirror is obliquely arranged on the shooting optical path.
Some digital single lens reflex cameras can select two types of focusing, i.e., a manual phase difference detection and a contrast detection (Japanese Patent Application, Publication No. 2001-275033). The phase difference detection determines focus when the mirror is obliquely provided on the shooting optical path, and the contrast detection determines focus using an output from the image-pickup device, when the mirror retreats from the image-taking optical path (Japanese Patent Application, Publication No. 2001-125173). A camera of Japanese Patent Application, Publication No. 2001-125173 electronically displays an image read from the image-pickup device on an electronic viewfinder (“EVF”), determines focus by the contrast detection, and measures the subject brightness using an output from the image-pickup device.
In general, the contrast detection seeks a position having a maximum AF evaluation value by slightly moving the image-taking lens in the optical axis direction, and disadvantageously requiring a long time to determine focus. On the other hand, the phase difference detection moves the image-taking lens by a detected defocus amount, and needs a shorter time to determine focus than the contrast detection.
Therefore, it is possible to construct the camera as follows for performing high-speed focus detection by the phase difference detection method in a case where the object image is observed with electric display.
The camera includes a main mirror whose whole portion is half-mirror and a sub-mirror which reflects light that has been transmitted through the main mirror, the main mirror and sub-mirror moving independently. The positions of the main mirror and sub-mirror are changed between the EVF state and the OVF state. Specifically, in the OVF state, the light flux that has come from the image-taking lens and reflected by the main mirror is led to the optical viewfinder, and the light flux that has been transmitted through the main mirror is reflected by the sub mirror and led to the focus detection unit. In the EVF state, the sub mirror is retreated from the image-taking optical path, the position of the main mirror is changed to reflect the light flux from the image-taking lens for leading it to the focus detection unit, and the light flux that has been transmitted through the main mirror is led to the image-pickup device.
The above-described structure makes it possible to perform focus detection of the focus detection unit by the phase difference detection method and high-speed focusing in the OVF and EVF states.
In the above-mentioned camera, since the photographer does not see into the optical viewfinder, outside light may enter the camera through the eyepiece of the viewfinder and reach the focus detection unit and image-pickup device. The light entered from the eyepiece (hereinafter, it is referred to as inversely-entering light) will become ghost light because it is not used for image-taking. Therefore, focus detection errors will occur when the inversely-entering light reaches the focus detection unit, and deterioration of the electrically-displayed image will occur when the inversely-entering light reaches the image-pickup device.
On the other hand, when the image-taking operation is performed from the OVF state or EVF state, since the main mirror and sub mirror are retreated from the image-taking optical path, the light flux from the image-taking lens reaches the image-pickup device directly. The arrival of the inversely-entering light in the image-pickup device during the image-taking operation deteriorates taken images.
It is possible to close an eyepiece shutter provided in the optical viewfinder to prevent the inversely-entering light from entering in the EVF mode and during an image-taking operation.
A camera has been proposed, in which the eyepiece shutter is closed with a mirror-up operation at the time of image-taking (see Japanese Patent Application, Publication No. H06-82908). The camera has a planetary mechanism that transmits driving power to the driving mechanism of the mirror and driving mechanism of the eyepiece shutter; the planetary mechanism drives the driving mechanism of the eyepiece shutter by its orbital motion.
Moreover, a camera has been proposed, in which the opening and shutting operation of the eyepiece shutter is controlled based on a detection result of photographer's viewing of the optical viewfinder (see Japanese Patent Application, Publication No. H08-234273). The camera has a viewing detection means that detects whether the eye of the photographer approaches the eyepiece of the optical viewfinder or not; the eyepiece shutter is closed when the eye of the photographer does not approach the eyepiece.
However, the camera proposed in Japanese Patent Application, Publication No. H06-82908 needs the mechanism that transmits driving power to the driving mechanism of the mirror and driving mechanism of the eyepiece shutter for preventing entrance of the inversely-entering light. Normally, the driving mechanism of the mirror and the driving mechanism of the eyepiece shutter are arranged separately because the driving mechanism of the mirror is arranged beside the mirror and the driving mechanism of the eyepiece shutter is arranged in the optical viewfinder. Therefore, the mechanism that transmits driving power to the two mechanisms becomes large and complicated.
Moreover, in the camera proposed in Japanese Patent Application, Publication No. H06-82908, the eyepiece shutter is not closed in the EVF state though it is closed with the image-taking operation. Therefore, to close the eyepiece shutter in the EVF mode, another driving mechanism or operation member that is operated by the photographer to drive the eyepiece shutter is needed.
However, providing the other driving mechanism increases in size of the camera and complicates the structure thereof because the other mechanism is added to the existing mechanisms.
Furthermore, in the case where the above-mentioned operation member is provided to the camera, the photographer must operate the operation member for each change between the OVF state and the EVF state; it bothers the photographer. In addition, since the photographer possibly forgets to operate the operation member in the EVF state, the eyepiece shutter does not always block the inversely-entering light. Moreover, opening the eyepiece shutter in the EVF state does not reflect the photographer's intention to close the eyepiece shutter when the optical viewfinder is not used.
On the other hand, in a case where the mechanism proposed in Japanese Patent Application, Publication No. H08-234273 is adopted for blocking the inversely-entering light in the EVF state, there is a problem that the eyepiece shutter is not closed when an image-taking operation is done from the OVF state. Specifically, in the case where the eyepiece shutter is not closed when the photographer takes an image while seeing into the optical viewfinder, the inversely-entering light may enter the camera from the eyepiece. In this case, the inversely-entering light reaches the image-pickup device, deteriorating the taken image.